1. Field of the Invention
The present invention relates to containers, particularly to stackable containers made from corrugated container board and having locking lids, such as are employed in the packaging of grapes and other soft fruits.
2. Description of the Prior Art
Prior U.S. patents of interest in connection with the presently described container are the following, considered together with the references cited therein:
______________________________________ U.S. Pat. No. Patentee Issue Date ______________________________________ 3,713,579 Chaffers January 30, 1973 3,820,706 Gibson et al June 28, 1974 4,245,773 Stollberg January 20, 1982 4,291,830 Sorensen September 29, 1981 4,304,351 Stollberg December 8, 1981 4,303,353 Stollberg December 8, 1981 ______________________________________
Of the foregoing, Chaffers U.S. Pat. No. 4,713,579 is of the greatest interest with respect to my presently described invention.
In the stackable container disclosed in the Chaffers patent, the stacking cleat extends above the plane of the lid. Its inner face is provided with a relief which also is located above the plane of the lid.
A mating, upwardly extending locking tab carried by the lid snaps into place in the relief when the lid is closed. This requires that the locking tab be bent substantially at right angles to the lid and that it remain in this deformed, upwardly extending position when the lid is closed.
It follows, therefore, that when the lid is opened, the opening forces a thrusting action against the locking tab in the plane of the tab, which usually is formed from corrugated paperboard. As a result, after one or two cycles of lid locking and unlocking, the tab delaminates, becomes dog-eared, and is no longer able to perform its locking function efficiently. Accordingly it is not possible to lock and unlock the lid of the container repeatedly, as is required during routine operations as the container contents are repeatedly inspected, dispensed, and stored.
Also, in the Chaffers container the lid is in two sections, and there are two spaced stacking cleats with associated locking means, one for each lid section. As a result, it is comparatively difficult and time consuming to stack the containers, since the spaced cleats must be precisely aligned each time one container is stacked upon the subjacent container.